Unit 5: Ch 15 (Autonomic NS & Visceral Reflexes)

Question 1

Visceral reflex arc

Answer 1

• Receptor
  
  • nerve endings that detect stretch, tissue damage, blood chemistry, body temp
• Afferent neurons
  
  • neurons that lead to the CNS
• Interneurons
  
  • integrating center in the CNS
• Efferent neurons
  
  • carry motor signals away from the CNS
• Effectors (3 possible)
  
  • cardiac muscle
  • smooth muscle
  • glands

Question 2

Autonomic nervous system (ANS)

Answer 2

• Manages involuntary processes responsible for the body’s homeostasis
  
  • Controls glands, cardiac muscle, and smooth muscle
  • Primary target organs: thoracic and abdominopelvic cavities
• 2 divisions
  
  • Sympathetic
  • Parasympathetic

Question 3

Parasympathetic division

Answer 3

• Decreases activity in all organs (except for digestion & urinary)
  
  • SLUDD
    
    • Salivation
    • Lacrimation
    • Urination
    • Digestion
    • Defecation
• Known as Rest or Digest
• Regulated activities
  
  • heart rate
  • bronchial constriction/airways
  • pupil size
• Only uses 1 neurotransmitter (ACh)

Question 4

Autonomic tone

Answer 4

• Balance of activity between the sympathetic and parasympathetic divisions
• Tones
  
  • Sympathetic tone
  • Parasympathetic tone

Question 5

Somatic pathways

Answer 5

• Where a motor neuron in the brainstem or spinal cord issues a myelinated axon that reaches a skeletal muscle

Question 6

Autonomic pathways

Answer 6

• Where a signal travels across 2 nerve fibers to reach the target organ, and it must cross a synapse, where these 2 neurons meet in an autonomic ganglion
  
  • Preganglionic fiber: begins with a neurosoma in the brainstem or spinal cord (myelinated)
  • Postganglionic fiber: axon from the 2nd neuron leaves the ganglion and extends the rest of the way to the target organ (unmyelinated)
• Secrets ACh or NE

Question 7

Sympathetic division

Answer 7

• Nerves arise from the thoracic and lumbar regions of the spinal cord
• Preganglionic neurosomas in lateral horn
• Postganglionic neurosomas: end in ganglia
• Axons exit the cord by way of spinal nerves T1 to L2 and lead to the nearby sympathetic chain
• Each paravertebral ganglion is connected to a spinal nerve by 2 branches: communicating rami
  
  • Preganglionic fibers: white communicating ramus (myelinated)
  • Postganglionic fibers: gray communicating ramus (unmyelinated)

Question 8

Adrenal glands

Answer 8

• Help secrete adrenaline
• 2 anatomical portions
  
  • Adrenal cortex
    
    • secretes supplemental steroid hormones
    • regulates mineralcorticoids and glucocorticoids
  • Adrenal medulla
    
    • chromaffin cells
    • secretes a mixture of hormones into the bloodstream
    • catecholamines
      
      • Epinephrine (adrenaline)
      • Norepinephrine (noradrenaline)

Question 9

Parasympathetic division

Answer 9

• Craniosacral division (cranial & sacral nerves)
• Preganglionic fibers
  
  • fibers in cranial nerves III, VII, IX, X
  • fibers arising from sacral spinal cord (S2-4)
• Terminal ganglia in or near target organs
• Less neuronal divergence than sympathetic division
• Ratio of fewer than 5 postganglionic fibers to every preganglionic fiber

Question 10

Parasympathetic NS

Answer 10

• Oculomotor (III)
  
  • Narrows pupil and focuses lens
• Facial n. (VII)
  
  • Lacrimal, nasal & salivary glands
• Glossopharyngeal n. (IX)
  
  • Parotid salivary gland
• Vagus n. (X)
  
  • Cardiac, pulmonary & esophageal plexus
  • Abdominal viscera including proximal colon
• Pelvic nerves
  
  • Distal half of colon, rectum, urinary bladder, and reproductive organs
• Note: opposite anatomical set-up as the sympathetic NS

Question 11

Neurotransmitters & their receptors

Answer 11

• ANS effects differ by chemical instruction and how the target cell is stimulated for 2 reasons
  
  • Different neurotransmitters
    
    • ACh: used by both parasympathetic & sympathetic NS, released by pre-ganglion neurons. In the parasympathetic NS it will also be released by post-ganglionic neurons
    • NE: used by sympathetic NS & is released by post-ganglion neurons
  • Different receptors
    
    • Cholinergic: binds with ACh
    • Adrenergic: binds with NE

Question 12

Neurotransmitters & their receptors (retitle?)

Answer 12

• Acetylcholine (ACh) is secreted by all pre-ganglionic neurons and post-ganglionic parasympathetic neurons, called cholinergic fibers
• 2 subdivisions of cholinergic receptors
  
  • Muscarinic receptors (that bind to ACh)
    
    • Cardiac muscle, smooth muscle, gland cells
    • Excitatory or inhibitory
  • Nicotinic receptors
    
    • Adrenal medulla and neuromuscular junctions of skeletal muscle
    • Excitatory

Question 13

Neurotransmitters & their receptors (retitle?)

Answer 13

• NE is secreted by almost all sympathetic post-ganglionic neurons, called adrenergic fibers
  
  • Receptors are called adrenergic receptors
• 2 subcategories of adrenergic receptors
  
  • Alpha-adrenergic receptors
    
    • Usually excitatory
    • 2 subclasses:
      
      • alpha_<u>1</u>: found in smooth muscle & regulates BP
      • alpha_<u>2</u>: found in brain & periphery. Inhibit NE & monitor sympathetic outflow
  • Beta-adrenergic receptors
    
    • Usually inhibitory
    • 2 subclasses:
      
      • ß_1: found in heart & helps increase heart rate and muscle contractility
      • ß_2: found in bronchials & smooth muscle

Question 14

Innervation

Answer 14

• Sympathetic effects tend to last longer than parasympathetic effects
  
  • Parasympathetic NS
    
    • enzyme
  • Sympathetic NS
    
    • reabsorption
    • diffusion

Question 15

Autonomic NS regulated by several levels of the CNS

Answer 15

• Cerebral cortex
• Hypothalamus
• Brainstem
• Spinal cord reflexes

Question 16

3 ways to end a signal from the ANS

Answer 16

• Enzyme that breaks down the actual neurotransmitter into different chemical components
• Diffusion
• Reabsorption

Question 17

Abdominal aortic plexus

Answer 17

• 3 major collateral ganglia
  
  • Celiac
  • Superior mesenteric
  • Inferior mesenteric